This happened during a demonstration.
What we have so far:
Video showing police lining up and civilians hiding behind a sign-holding shelter. A female gets shot and falls to the ground.
https://www.facebook.com/groups/428802038569425/posts/434923727957256/
Close-up images of the police and weapons in the video above. An image of the victim wounded and her helmet.
https://twitter.com/1DPotato14/status/1359556078111973376?s=20
Another video confirms the footage from a slightly different angle and shows the victim’s body being carried from the shelter.
https://twitter.com/Maung94432290/status/1359124473765457922?s=20
There is also an alleged brain scan and more information on the victim and alleged shooter
https://www.facebook.com/phyo.h.paing/posts/4222596397769611
The exterior of helmet
https://www.facebook.com/ko.linlin.372/posts/2943606049251179
This incident was briefly covered in a Reuters piece:
https://www.reuters.com/article/us-myanmar-politics/myanmar-police-fire-to-disperse-protest-four-hurt-one-critical-idUSKBN2A9061
Social media reporting alleges that the shooter is a police commander.
More information can be seen, in Burmese, at this link.